The patch titled
i386: extend alternative instructions framework
has been added to the -mm tree. Its filename is
i386-extend-alternative-instructions-framework.patch
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See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: i386: extend alternative instructions framework
From: Joerg Roedel <joerg.roedel@xxxxxxx>
This series of patches extend the alternative instructions framework on i386
and x86_64 architectures to support two alternative instruction replacements.
This code is used together with the introduction of the X86_FEATURE_SYNC_RDTSC
flag on i386 to simplify and optimize the get_cycles_sync() function. The
optimization changes this function to use RDTSCP instead of CPUID;RDTSC if
this instruction is available. Don't use CPUID there is really important if
the kernel runs as a KVM guest, because this instruction is intercepted and
causes an expensive VMEXIT.
This patch extends the alternative instructions framework to support 2
alternative instructions.
Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/alternative.c | 21 +++++++++++-----
include/asm-i386/alternative.h | 40 +++++++++++++++++++++++++++++--
2 files changed, 53 insertions(+), 8 deletions(-)
diff -puN arch/i386/kernel/alternative.c~i386-extend-alternative-instructions-framework arch/i386/kernel/alternative.c
--- a/arch/i386/kernel/alternative.c~i386-extend-alternative-instructions-framework
+++ a/arch/i386/kernel/alternative.c
@@ -153,14 +153,23 @@ extern u8 __smp_alt_begin[], __smp_alt_e
void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
{
struct alt_instr *a;
- u8 *instr;
+ u8 *instr, *replacement;
+ u8 replacementlen;
int diff;
DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end);
for (a = start; a < end; a++) {
- BUG_ON(a->replacementlen > a->instrlen);
- if (!boot_cpu_has(a->cpuid))
+ if (boot_cpu_has(a->cpuid)) {
+ replacement = a->replacement;
+ replacementlen = a->replacementlen;
+ } else if ((a->replacementlen2 > 0) &&
+ (boot_cpu_has(a->cpuid2))) {
+ replacement = a->replacement2;
+ replacementlen = a->replacementlen2;
+ } else
continue;
+
+ BUG_ON(replacementlen > a->instrlen);
instr = a->instr;
#ifdef CONFIG_X86_64
/* vsyscall code is not mapped yet. resolve it manually. */
@@ -170,9 +179,9 @@ void apply_alternatives(struct alt_instr
__FUNCTION__, a->instr, instr);
}
#endif
- memcpy(instr, a->replacement, a->replacementlen);
- diff = a->instrlen - a->replacementlen;
- nop_out(instr + a->replacementlen, diff);
+ memcpy(instr, replacement, replacementlen);
+ diff = a->instrlen - replacementlen;
+ nop_out(instr + replacementlen, diff);
}
}
diff -puN include/asm-i386/alternative.h~i386-extend-alternative-instructions-framework include/asm-i386/alternative.h
--- a/include/asm-i386/alternative.h~i386-extend-alternative-instructions-framework
+++ a/include/asm-i386/alternative.h
@@ -10,11 +10,14 @@
struct alt_instr {
u8 *instr; /* original instruction */
u8 *replacement;
+ u8 *replacement2;
u8 cpuid; /* cpuid bit set for replacement */
+ u8 cpuid2; /* cpuid bit set for replacement2 */
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction, <= instrlen */
- u8 pad;
-};
+ u8 replacementlen2;
+ u8 pad[3];
+} __attribute__ ((packed));
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
@@ -36,6 +39,12 @@ static inline void alternatives_smp_swit
#endif
/*
+ * use this macro(s) if you need more than one output parameter
+ * in alternative_io_*
+ */
+#define ASM_OUTPUT2(a, b) a, b
+
+/*
* Alternative instructions for different CPU types or capabilities.
*
* This allows to use optimized instructions even on generic binary
@@ -53,9 +62,12 @@ static inline void alternatives_smp_swit
" .align 4\n" \
" .long 661b\n" /* label */ \
" .long 663f\n" /* new instruction */ \
+ " .long 0x00\n" \
" .byte %c0\n" /* feature bit */ \
+ " .byte 0x00\n" \
" .byte 662b-661b\n" /* sourcelen */ \
" .byte 664f-663f\n" /* replacementlen */ \
+ " .byte 0x00\n" \
".previous\n" \
".section .altinstr_replacement,\"ax\"\n" \
"663:\n\t" newinstr "\n664:\n" /* replacement */\
@@ -77,14 +89,38 @@ static inline void alternatives_smp_swit
" .align 4\n" \
" .long 661b\n" /* label */ \
" .long 663f\n" /* new instruction */ \
+ " .long 0x00\n" \
" .byte %c0\n" /* feature bit */ \
+ " .byte 0x00\n" \
" .byte 662b-661b\n" /* sourcelen */ \
" .byte 664f-663f\n" /* replacementlen */ \
+ " .byte 0x00\n" \
".previous\n" \
".section .altinstr_replacement,\"ax\"\n" \
"663:\n\t" newinstr "\n664:\n" /* replacement */\
".previous" :: "i" (feature), ##input)
+/* Like alternative_io, but supports 2 possible alternatives */
+#define alternative_io_two(oldinstr, newinstr, feat, newinstr2, feat2,\
+ output, input...) \
+ asm volatile ("661:\n\t" oldinstr "\n662:\n" \
+ ".section .altinstructions,\"a\"\n" \
+ " .align 4\n" \
+ " .long 661b\n" /* label */ \
+ " .long 663f\n" /* new instruction */ \
+ " .long 665f\n" /* new instruction 2 */\
+ " .byte %c[f]\n" /* feature bit */ \
+ " .byte %c[f2]\n" /* feature bit 2*/ \
+ " .byte 662b-661b\n" /* sourcelen */ \
+ " .byte 664f-663f\n" /* replacementlen */ \
+ " .byte 666f-665f\n" /* replacementlen 2 */\
+ ".previous\n" \
+ ".section .altinstr_replacement,\"ax\"\n" \
+ "663:\n\t" newinstr "\n664:\n" /* replacement */ \
+ "665:\n\t" newinstr2 "\n666:\n" /* replacement2 */ \
+ ".previous" : output : [f] "i" (feat), \
+ [f2] "i" (feat2),##input)
+
/*
* Alternative inline assembly for SMP.
*
_
Patches currently in -mm which might be from joerg.roedel@xxxxxxx are
git-kvm.patch
remove-constant_tsc-reporting-from-proc-cpuinfo-power.patch
i386-extend-alternative-instructions-framework.patch
x86_64-changes-to-x86_64-architecture-for.patch
i386-add-the-x86_feature_sync_rdtsc-flag.patch
optimize-and-simplify-get_cycles_sync.patch
-
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